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High-K fertilizer for cacti?

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High-K fertilizer for cacti?

Postby Steve Johnson » Sat Jan 21, 2012 11:45 pm

I'm sitting on my hands as I wait for the new growing season, so I wanted to prepare some notes. Based on research I looked up at Cactuspedia, I have a few cacti which indicate the need for a high-potassium fertilizer when they get fed over the summer. They are as follows: Eriosyce senilis, Gymnocalycium ochoterenae ssp. vatteri, and Mammilaria microcarpus. Unfortunately Cactuspedia didn't have cultivation pages on those specific species of Gymno and Mamm, so I had to guess by what I thought might be similar enough with other species for their feeding habits.

Assuming that Cactuspedia is reliable, I can say for sure about E. senilis. How about the Gymno and Mamm species I have? Also, what would be a good recommendation for an appropriate high-potassium fertilizer? I'll be using the MSU orchid fertilizer, but I didn't know if it would fill the bill for cacti that need a high-K feeding.

Thanks for any help on this!

Steve
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Postby peterb » Sun Jan 22, 2012 3:16 am

Cactuspedia is not reliable. :-)

Just use the same fertilizer on everything. Dilute 20-20-20 every now and then or 2-2-7 all the time.

There is no Mammillaria microcarpus and no Gymnocalycium ochteranae. Mammillaria microcarpa, yes. Echinofossulocactus ochoteranus, yep.

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Postby luddhus » Sun Jan 22, 2012 5:02 am

Gymnocalycium ochoterenae is listed in all important cactus books I have, and on the species list on this site as well.
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Postby Steve Johnson » Sun Jan 22, 2012 5:30 am

luddhus wrote:Gymnocalycium ochoterenae is listed in all important cactus books I have, and on the species list on this site as well.

Same here. With that said, I've barely started relearning what I used to know about cactus taxonomy, so I have to rely on the tags that come with the plants I buy at the California Cactus Center. A couple of boo-boos I found were obvious -- for example the CCC tags matanzus as Matucana, when it's clearly Melocactus. That one mystifies me. Other boo-boos aren't so obvious, although maybe I don't have enough brain cells to figure out the taxonomical confusion anymore.

Getting back to the matter at hand, I realize that a lot of info on the internet is bullplop. Is it indeed correct that Cactuspedia was misinformed about certain cacti needing a particular "high potassium" fertilizer?
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Postby luddhus » Sun Jan 22, 2012 6:50 am

Steve Johnson wrote:Is it indeed correct that Cactuspedia was misinformed about certain cacti needing a particular "high potassium" fertilizer?


Depends on why they wrote it. Did they quote a source? (I have not yet found this "information" on Cactuspedia, so I cannot check.)
I have never heard of cacti that need more potassium than other species.

Besides, it is "matanzanus".
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Postby Steve Johnson » Sun Jan 22, 2012 8:12 am

luddhus wrote:Depends on why they wrote it. Did they quote a source? (I have not yet found this "information" on Cactuspedia, so I cannot check.)
I have never heard of cacti that need more potassium than other species.

Besides, it is "matanzanus".

Cactuspedia doesn't quote any sources, so the online community there is something I realize has to be taken with more than a few grains of salt. Wish I had more time to search out reliable authorities, but there you go.

By the way, I may have misunderstood what I was trying to say. The plant tag I got from the CCC said Matucana matanzus, but I know it's Melocactus matanzus. Why they put it down as Matucana I have no idea.
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Postby iann » Sun Jan 22, 2012 11:36 am

Feeding habits for all small globular cacti is the same. Dilute and not too often ;) Or *very* dilute and as often as you like :lol:

The advice for "high potassium" is a mixture of folklore about getting a cactus to flower, and a safety net for over-feeders. If you're going to over-feed then best to use a low-nitrogen mix.
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Postby luddhus » Sun Jan 22, 2012 11:51 am

Steve Johnson wrote:but I know it's Melocactus matanzus.


I meant that the correct spelling is "Melocactus matanzanus". :)
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Postby peterb » Sun Jan 22, 2012 5:51 pm

Sorry about that Gymnocalycium thing.

Yes, it is bull pop.

Ian's rule of thumb is correct.

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Postby Steve Johnson » Sun Jan 22, 2012 7:23 pm

peterb wrote:Sorry about that Gymnocalycium thing.

Yes, it is bull pop.

Ian's rule of thumb is correct.

peterb

Okay, it's a good thing I keep my skeptical hat on so I can find out what different sources have to say before I steer into any wrong directions. This was really helpful -- thanks, guys!
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Postby A. Dean Stock » Mon Jan 23, 2012 5:25 am

The MSU orchid fertlizer (as Iann says;very dilute)works well for me on Opuntia species but I have few other cacti. I grow a few Escobaria and Echinocereus native to this area as well and all seem to do very well on this fertilizer. Orchid culture is somewhat more demanding of good water and proper fertilizer than cacti but many of their requirements are similar. I only fertilize my cacti twice a year at most and with about 1/2 tsp/gal of the MSU fertlizer. Most of my cacti would grow fine without the fertilizer but I get almost double the pad development and flowers with the additon of the fertilizer given after good growth starts in the spring.
I should point out that all my cacti are outside "in ground" and not potted.
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Postby Peterthecactusguy » Mon Jan 23, 2012 12:04 pm

I add fertilizer to my outdoors cacti (Opuntia mostly) when they are ready to bloom to get them to produce fruits. I don't know if it works or not. (I use the Schultz cacti fertlizer). I also use that for all my potted plants every other watering and it seems to work fine and is a very low fertilizer. I Think it's 2-2-2 but I might be mistaken.
Here's to you, all you insidious creatures of green..er I mean cacti.
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Postby iann » Mon Jan 23, 2012 2:41 pm

a very low fertilizer. I Think it's 2-2-2

Equals 20-20-20 plus a lot of filler ;)
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